Dental prosthesis manufacturing process, dental prosthesis pattern &amp; dental prosthesis made thereby

ABSTRACT

A dental prosthesis is made by first forming a model of a patient&#39;s dentition. A three dimensional digital data corresponding to the surfaces of the model is then created. Based on this data, a three dimensional digital data file is then created substantially corresponding to the dental prosthesis to be manufactured. The three dimensional digital data of the dental prosthesis to be manufactured is next transmitted to automated prototyping equipment, and using the automated prototyping equipment, a wax pattern of the dental prosthesis is manufactured based upon this three dimensional digital data of the dental prosthesis. Finally, using this wax pattern in the lost wax investment casting process, the dental prosthesis is made. Prior to investment casting, marginal edges of the wax pattern are adjusted manually.

RELATED PATENT APPLICATION & INCORPORATION BY REFERENCE

This application is a continuation application of U.S. Ser. No.09/656,255, entitled “DENTAL PROSTHESIS MANUFACTURING PROCESS, DENTALPROSTHESIS PATTERN & DENTAL PROSTHESIS MADE THEREBY,” filed Sep. 6,2000, herein parent application, now U.S. Pat. No. ______. This parentapplication is incorporated herein by reference and made a part of thisapplication. Moreover, the inventors incorporate herein by reference anyand all U.S. patents, U.S. patent applications, and other documents,hard copy or electronic, cited or referred to in this continuation, orthe above-identified, parent application.

BACKGROUND OF THE INVENTION

Computer technology has advanced to the point where a dental prosthesismay be milled from a solid block of material based on three-dimensionaldigital data corresponding to a proposed shape of the dental prosthesis.The dentist first makes an impression of a patient's existing dentition.Typically, this includes nearby surfaces where the prosthesis is to belocated in the patient's mouth. This is accomplished by the dentistfirst drilling away any unwanted dental tooth structure and then havingthe patient bite into an impression material that forms a negativeimpression of the patient's dentition, including the tooth structure towhich the dental prosthesis is to be attached. This negative impressionis then filled with dental die stone to make a model of the toothstructure to which the dental prosthesis is to be attached and adjacentteeth, particularly the teeth immediately above and to the sides of thetooth structure to which the dental prosthesis is to be attached. Thismodel of the patient's dentition captures an impression of the occlusionsurfaces between upper and lower aligned teeth and the configuration ofthe tooth structure to which the dental prosthesis is to be attached.

The computer aided design equipment used to make a dental prosthesis hasan scanner that is used to scan the surfaces of the model. Scanning maybe accomplished either with optical techniques using laser or non-laserlight or tactile techniques where a probe physically contacts thetooth's surface. The computer aided design equipment converts themodel's surfaces into three-dimensional digital data corresponding tothe physical shape of the model. This original data collected duringscanning is then used to create an image of the proposed shape for theprosthesis on a screen of a computer monitor. The computer aided designequipment is programmed to allow the user, with the aid of a mouse andemploying conventional point and click techniques, to change the shapeof the image. The original image displayed on the monitor screen needsto be adjusted to modify the original image to correspond to theultimate shape of the dental prosthesis.

Because the data originally collected during scanning isn't preciseenough to make the dental prosthesis directly based on this data, theuser can and does make adjustments to the data originally provided bythe scanner so that the dental prosthesis, at least in theory, fitsproperly into the patient's mouth. After making such adjustments to thedata collected by the scanner, the adjusted three-dimensional digitaldata is then forwarded to an automatic milling machine which then millsaway the unwanted material from a block to form the dental prosthesis.Typically, the block of material is a ceramic, titanium, or compositeplastic material. One of the perceived advantages of this technique isthe elimination of conventional investment casting of a wax pattern ofthe dental prosthesis, which has conventionally been used to make adental prosthesis.

Although this computer aided design equipment proposes to eliminateconventional investment casting, it suffers from a number of drawbacksthat prevent greater utilization of this technology. First, it isimpractical to make dental prosthesis from such precious metals as goldand platinum using this technology because so much of the precious metalis lost during the milling process. Second, the adjustments made to theimage based on the original data collected during scanning usually failto create a dental prosthesis that properly fits into the patient'smouth. The inaccuracies in the shape of the dental prosthesis soproduced using this technology are particularly acute along the marginaledges of the prosthesis adjacent the margins where the treated (drilled)tooth surfaces of an individual tooth are contiguous with the untreated(undrilled) tooth surfaces of this individual tooth.

SUMMARY OF THE INVENTION

This invention overcomes the drawbacks associated with the computeraided design technology that eliminates investment casting of a dentalprosthesis and directly mills the prosthesis from a block of material.It has several features, no single one of which is solely responsiblefor its desirable attributes. Without limiting the scope of thisinvention as expressed by the claims that follow, its more prominentfeatures will now be discussed briefly. After considering thisdiscussion, and particularly after reading the section entitled,“DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT,” one will understandhow the features of this invention provide its benefits, which include,but are not limited to,

-   -   (1) usage of precious metal in making a dental prosthesis with        minimum waste of such metal,    -   (2) improved accuracy of the marginal edges of the dental        prosthesis positioned along the margins of a tooth structure,        and    -   (3) reduction of time to make a dental prosthesis using        conventional investment casting techniques.

The invention includes a method of manufacturing a pattern of a dentalprosthesis from a wax material, a method of manufacturing a dentalprosthesis itself using this pattern, the dental prosthesis itself, andthe pattern used in the manufacture of the dental prosthesis. As usedherein, a dental prosthesis includes wax-ups (a term used in theindustry) of articulated jaws. These wax-ups constitute an entire arrayof the teeth in an individual patient and they are used for diagnosticpurposes. As used herein, “wax material” includes waxes, thermoplastics,combinations of wax and thermoplastic, or other ablative materials thatare commonly used in the lost wax process.

The first step of the method of this invention is to form a model of apatient's dentition. This model includes surfaces corresponding to thedental structure nearby the location that the dental prosthesis is to beplaced in the mouth of a patient.

The second step is to create three dimensional digital datacorresponding to these surfaces, and based at least in part on thisdata, to create three dimensional digital data substantiallycorresponding to the dental prosthesis to be manufactured. Typicallythis is accomplished using a scanner to scan the surfaces of the modelto collect three dimensional digital data corresponding to thesesurfaces. A monitor screen of computer aided design equipment displaysan image of a proposed dental prosthesis based, at least in part, on thecollected three dimensional digital data corresponding to the surfacesof the model. With the aid of the computer aided design equipment, theimage is modified so that the modified image displayed on the monitorscreen substantially corresponds to the dental prosthesis to bemanufactured.

The third step is to transmit the three dimensional digital data of thedental prosthesis to be manufactured to automated prototyping equipment.Using the automated prototyping equipment, a wax pattern of the dentalprosthesis is made from a wax material. This pattern is then used in thelost wax investment casting process to manufacture the dentalprosthesis.

In accordance with this invention, the pattern has marginal edges thatare at least ¾ of a millimeter from margins of an individual toothstructure to which the dental prosthesis is to be attached. These setback marginal edges of the pattern are manually adjusted to compensatefor the specific configuration of the individual tooth structure byadding wax material to these set back marginal edges. This insures thatthe inaccuracies ordinarily occurring using computer aided design andmilling equipment are avoided.

DESCRIPTION OF THF DRAWING

The preferred embodiment of this invention, illustrating all itsfeatures, will now be discussed in detail. This embodiment depicts thenovel and non-obvious method of manufacturing a pattern of a dentalprosthesis from a thermoplastic material, and pattern and dentalprosthesis made by this method, as shown in the accompanying drawing,which is for illustrative purposes only. This drawing includes thefollowing figures (Figs.), with like numerals indicating like parts:

FIG. 1 is a perspective view of the upper jaw portion of a model for apatient's dentition.

FIG. 1A is an enlarged fragmentary view of part of the upper jaw portionof the model for a patient's dentition shown in FIG. 1, depicting astump on which a crown type dental prosthesis is to be attached.

FIG. 2 is the monitor screen of computer aided design equipmentprogrammed to create images of different shaped dental prosthesis.

FIG. 3 is the monitor screen of computer aided design equipmentdisplaying how different portions of an image of a dental prosthesis maybe modified.

FIG. 4 is another view of the monitor screen showing a dental prosthesismounted to a tooth structure.

FIG. 5 is a schematic diagram of computer aided design equipment used inthe method of this invention.

FIG. 6 is a side elevational view of a treated tooth structure to whicha crown type dental prosthesis is to be attached.

FIG. 7 is a schematic diagram of computer aided design equipmentconnected to automated prototyping equipment that makes a pattern(referred to herein as wax pattern) of the dental prosthesis from waxmaterial.

FIG. 8 is a schematic cross-sectional view showing a wax pattern of acrown type dental prosthesis positioned in a casting ring used ininvestment casting.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with conventional techniques, a model of a patient'sdentition is made. The upper jaw portion 10 of such a model is shown inFIG. 1. A lower jaw portion of this model is also used to collect toothsurface data, but is not shown. For purposes of illustration as shown inFIG. 6, an actual stump 32 to which a crown type 50 a dental prosthesisis to be attached includes a drilled away portion 32 a and anundisturbed portion 32 b next to the patient's gum 34. Where thecontiguous borders of the portions 32 a and 32 b meet, as defined by theline 38, a margin is formed. The jaw portion 10 includes a replicate 32a of the stump 32 to which the crown type dental prosthesis 50 a is tobe attached.

As shown in FIG. 6, computer aided design equipment 19 creates an imageof a dental prosthesis based on data collected from the model of thepatient's dentition. As illustrated in FIG. 7, computer aided designequipment sold under the trademark LabQraft™ by DentalmaticTechnologies, Inc. of St. Laurent, Quebec, Canada is modified inaccordance with this invention to eliminate milling apparatus connectedto an output 19 a. In accordance with this invention, this output 19 ais connected to automated prototyping equipment 23. Other similar typeequipment such as sold by Decim AB of Skelleftea, Sweden, may also bemodified by eliminating the milling equipment and used in accordancewith this invention. Suitable automated prototyping equipment 23 is soldunder the trademark ModelMaker II™ by Sanders Prototype, Inc. ofMerrimack, N.H.

The equipment 19 includes an optical scanner 20 that scans the surfacesof the model of a patient's dentition by directing a beam of light froma source 17 at the model's surfaces, for example, at the tooth surfacesof the upper jaw portion 10. The reflected light represents informationcorresponding to the contours of these surfaces. This information iscollected by a sensor 15 and then stored in the memory 22 of a computer24 as three dimensional digital data. Various images of a dentalprosthesis are displayed on a screen 18 of a monitor 30 connected to anoutput 32 of the computer 24 based on the data originally collected bythe scanner 20. These images, and the corresponding data creating theseimages, are modified by the user using conventional input devices suchas a mouse 26 and keyboard 28 to interact with, and modify, theoriginally collected three dimensional digital data.

The numeral 12 is an image displayed on the screen 18 corresponding tothe actual tooth structure, that is, the stump 32 (FIG. 6) that has beenprepared by a dentist for a dental prosthesis. The image 12 is createdupon optically scanning the surface of the replicate 32 a of the stump32 and manipulating the collected information of the surface contours,creating the image 12 in accordance with a program 24 a that controlsprocessing of the data by the computer 24. As depicted in FIGS. 3 and 4,an image 14 of the crown 50 a to be attached to the stump 32 isdisplayed on the monitor's screen 18. In this example, an image 40 ofthe surface of an upper tooth immediately above and facing the stump 32and an image 42 of the surface of the upper adjacent tooth are alsodisplayed on the monitor's screen 18. Through the use of the mouse 26and keyboard 28 the user can change parameters such as die spacer,minimum thickness of the prosthesis, contact points, grooves, cuspoverlays and marginal ridges.

In accordance with this invention, the automated prototyping equipment23 makes a wax pattern 50 (FIGS. 7 and 8) from wax material. This waxpattern 50 is based on the data collected during optical scanning.Typically, the pattern 50 is formed by a series of wax layers laid oneupon another until the desired overall shape is completed. The waxpattern 50 formed by the method of this invention is at least ¾millimeters from the margin line 38 a corresponding to the actual marginline 38 as determined when the pattern 50 is seated by a dentaltechnician on the replicate 32 a of a stump 32. In other words, when theuser is creating on the monitor screen 18 an image 14 of the crown 50 a,the edges 14 a of this image 14 are at least ¾ of a millimeter from animage 38 a of the margin line displayed on the screen 18. Consequently,the wax pattern 50 has marginal edges 51 that are displaced at least ¾millimeters from the margin line 38 a on the replicate 32 a thatcorrespond to the actual margin line 38. In accordance with thisinvention, the edges 51 of the pattern 50 are then manually adjusted tocompensate for the specific configuration of the stump 32 by adding awax material to these edges. This avoids the inaccuracies associatedwith attempting to make a dental prosthesis that fits properly basedsolely on computer manipulation of data and then milling the prosthesisfrom a block of material as dictated by this data.

The wax pattern 50 produced by the automated prototyping equipment 23 isused in the conventional investment casting process to make the crowntype dental prosthesis 50 a. As shown in FIG. 8, the wax pattern 50 isattached to a sprue 60 made of wax material. This sprue 60 is mounted toa raised conical portion of a rubber base 62 and a metal ring 64 linedwith a sheet 68 of ceramic fiber paper is seated on the base.Preferably, a wax rod 70 extends from a side portion of the pattern 50to the base 62. The hollow interior 64 a of the ring 64 and base 62 isthen filled with the investment material, for example, a plaster, thatis allowed to dry. After drying the assembly of the base 62, ring 64 andmounted wax pattern 50 is inverted and the base removed. The sprue 60and wax pattern 50 are next removed by burning them away so that thecasting is formed with a hollow cavity (not shown) into which moltenmetal is poured to form the crown 50 a.

SCOPE OF THE INVENTION

The above presents a description of the best mode contemplated ofcarrying out the present invention, and of the manner and process ofmaking and using it, in such full, clear, concise, and exact terms as toenable any person skilled in the art to which it pertains to make anduse this invention. This invention is, however, susceptible tomodifications and alternate constructions from that discussed abovewhich are fully equivalent. For example, although only crowns have beenillustrated, other dental prosthesis such as, for example, bridges andinlays can be made using this invention. Moreover, this method may alsobe used to make wax-ups of articulated jaws used for diagnosticpurposes. Consequently, it is not the intention to limit this inventionto the particular embodiment disclosed. On the contrary, the intentionis to cover all modifications and alternate constructions coming withinthe spirit and scope of the invention as generally expressed by thefollowing claims, which particularly point out and distinctly claim thesubject matter of the invention:

1. A method of manufacturing a pattern of a dental prosthesis,comprising the steps of (a) collecting data substantially correspondingto an image of the dental prosthesis to be manufactured and transmittingsaid data to automated prototyping equipment, and (b) using theautomated prototyping equipment, making the pattern of said dentalprosthesis to be manufactured based upon said data.
 2. A method ofmanufacturing a dental prosthesis, comprising the steps of (a)collecting data substantially corresponding to an image of the dentalprosthesis to be manufactured and transmitting said data to automatedprototyping equipment, and (b) using the automated prototypingequipment, making from a wax material a pattern of said dentalprosthesis to be manufactured based upon said data, and (c) using saidpattern in the lost wax investment casting process manufacturing saiddental prosthesis.
 3. A method of manufacturing a pattern of a dentalprosthesis, comprising the steps of (a) collecting data substantiallycorresponding to an image of the dental prosthesis to be manufacturedand transmitting said data to automated prototyping equipment, and (b)using the automated prototyping equipment, making the pattern of saiddental prosthesis to be manufactured based upon said data, said patternhaving marginal edges that are at least ¾ of a millimeter from marginsof an individual tooth structure to which the dental prosthesis is to beattached.
 4. The method of claim 3 where the marginal edges of thepattern are manually adjusted to compensate for the specificconfiguration of said individual tooth structure.
 5. The pattern of adental prosthesis made by (a) collecting data substantiallycorresponding to an image of the dental prosthesis to be manufacturedand transmitting said data to automated prototyping equipment, and (b)using the automated prototyping equipment, making the pattern of saiddental prosthesis to be manufactured based upon said data.
 6. The dentalprosthesis made by (a) collecting data substantially corresponding to animage of the dental prosthesis to be manufactured and transmitting saiddata to automated prototyping equipment, and (b) using the automatedprototyping equipment, making from a wax material a pattern of saiddental prosthesis to be manufactured based upon said data, and (c) usingsaid pattern in the lost wax investment casting process manufacturingsaid dental prosthesis.